Image forming devices move media sheets throughout a media path. The media sheets are moved along the media path past one or more imaging stations where an image is transferred to the sheet. The media path may further include a duplexer. A duplexer is a device that receives a media sheet from the forming device, inverts the sheet, and then conveys the sheet back to the imaging stations for an image to be formed on the second side. The sheet may or may not have an image formed on the first side when the sheet is received by the duplexer.
Correct positioning and alignment is necessary for the image to be accurately transferred to the media sheets. Misalignment of the media sheets when moving past one or more of the imaging stations may cause the image formed on the media sheet to be misaligned resulting in a print defect. Further, an excessive amount of skew within the media sheet may cause a media jam. Clearing a media jam requires the operator to manually remove the jammed media sheets from the media path and reset the image forming device.
Image forming devices are capable of forming images of various types on various types of media sheets. Each of the media sheets has different physical characteristics that affect the way the media sheets move along the media path. The media path may be calibrated to accurately move one type of media sheet, but cause skew when moving a second type of media sheet.
Determining the amount of skew on a media sheet moving through a media path may be difficult. It may be necessary to position one or more sensors along the media path to detect the amount of skew. However, sensors may incorrectly determine the amount of skew on the media sheet. Additionally, sensors are expensive. Many purchasers of image forming devices make their purchasing decisions based mainly on cost. Therefore, any unnecessary costs are preferably removed to make the device more attractive to the purchaser.